FOTOSINTESIS12

8/10/2019 FOTOSINTESIS12

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FOTOSINTESIS


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Fotosintesis ?

Reaksi fotokimia

Bhn baku : CO2 & H2O

Dg energi surya

Sintesis gula

Pd jar fotosintetik

Konversi energi surya

Energi kimia


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Fotosintesis bakteri belerang

Sumber energi : Foto Sumber (donor)

hidrogen dan elektron

berupa H2S, bukan

H2O

H2S + CO2CH2O + 2S

Perangkat fotosintesis

Van Neil


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Percobaan JAN INGENHOUSZ

Gas O2 dilepaskan

Matahari dibutuhkan

Bagian yang berhijaudaun saja yang

melepaskan O2


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Epidermis

Berkas

angkutan

Palisade

Epidermis & lapisan

kutikula

Bunga karang

Struktur daun


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Chloroplast Structure

Chlorophyll pigment is embedded in the thylakoid

membrane

Where within this organelle is the

chlorophyll pigment located?


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Jenis sinar efektif untuk fotosintesis

h . c

E = h v = -----

Ket. : E= energi foton; h = konstanta planck (6.62x 10-27 erg/dt)

c = kecepatan cahaya ( 3. 105 km / dt )

= panjang gelombang sinar ; v= frekuensi


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Absorption Spectra

In the thylakoid, several pigments differ in theirabsorption spectrum.

Chlorophyll a(dominant pigment) absorbs best in

the red and blue wavelengths, and least in thegreen.

Other pigments(chll b, carotenoids)

have differentabsorption spectra and

can transfer energy to chll a


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Prinsip Penyerapan Sinar

Sinar diserapSpektrum sinar tampak

Energi : Quanta / foton

Penyerapan sinarHkm Stark Einstein

Bbrp molekul menyerap 1 foton

Foton menimbulkan eksitasi

Eksitasi hasilkan tk energi final utk transfer elektron

Lama keadaan pigmen tereksitasi = 1/10-9dt

Sbgn energi eksitasi hilang sbg panas & fluoresens


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Perangkat Fotosintesis Tbhn Tinggi

1. Daun Jaringan Mesofil sel mesofil kloroplas

2. KloroplasGrana & Stroma

Pd Grana : Penangkap energi suryaReaksi terang

1. Fotosistem (I & II)

2. Aseptor elektron

3. Perangkat Pendukung

a. Ligth Harvesting Complex

b. Penghubung PSIIPS I

3. Sumber energi : Cahaya Mthr; Sumber elektron : H2O


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Perangkat fotosistem (FS)

FS II:

1. P680 (Pusat reaksi)

2. Klorofil a (dominan)

3. Klorofil-b (sedikit / tdk ada)

4. Feofitin

5. Quinon

LHC :ligth harvesting complex

Fungsi : Reaksi fotokimia

1. Foto-oksidasi air (fotolisis)

2. Reduksi plastoquinon

15Polipeptida & 9 komp. redoks(Klo, feo, plasto quinon, Mn,

Fe, Cyt-b559, Karoten)

FS I :

1. P700 (Pusat reaksi)

2. Klorofil a (dominan)

Klorofil b (sedikit)

3. Fe-S protein

4. Ferredoxin

LHC (Klo a, klo b, xantofil + sedikitkaroten)

Fungsi :

1. Oksidasi plastocyanin &

Cu-protein

2. Reduksi ferredoxin dan Fe-

S protein.


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Efek Penguatan Emerson


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Struktur kloroplas

PadaThylakoid membrane : Terjadi reaksi-reaksi cahaya

Pada matrik stroma: terjadi reaksi gelap


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TAHAPAN FOTOSINTESIS

Reaksi Cahaya [Terang]:

1. Fotolisis air

2. Fotofosforilasimembentuk ATP (siklik & non siklik)

3. Reduksi NADP menjadi NADPH2 (non siklik)

Reaksi Gelap: [ Daur Calvin, RPP, PCR]1. Pengikatan CO2 (Fiksasi CO2)karboksilasi

2. Reduksi gula pentosa (5-C : RudP)

3. Regenerasi : pembentukan kembali senyawa antara

fotosintesis (gula pentosa)

4. Otokatalisis : Pembentukan gula (6-C) dari setiap 6 CO2

yang diikatnya.


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Reaksi pada membran tilakoid


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Gambaran umum fotosintesis di kloroplas

Reaksi cahaya Reaksi gelap


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Steps to Non-cyclic Electron Flow

1. P680 absorbs light

2. Light excites 2e-and

passes e- to primaryelectron acceptor

3. Water is split into

O2

oxygen gasH+to thylakoid space

2e- resuppliesP680


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4. e- pass through

ETC, where they

fall in E

5. E from e- iscaptured to

produce ~ 1.5 ATPs

through

chemiosmotic

phosphorylation


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6. e- from P680

replenish e- in P700

7. e- in P700 are

excited again by

light and passed to

a primary electron

acceptor


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8. e- cascadesdown short ETC,where e-

combine withand reduceNADP+and H+to form NADPH(E richmolecule)


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Non-Cyclic Electron Flow

ATP and

NADPH

created in

the LightReactions

are used

in theCalvin

Cycle
http://localhost/var/www/apps/Desktop/Ch_10_Photosynthesis/10-17-LightReactions.movhttp://localhost/var/www/apps/Desktop/Ch_10_Photosynthesis/10-17-LightReactions.movhttp://localhost/var/www/apps/Desktop/Ch_10_Photosynthesis/10-17-LightReactions.movhttp://localhost/var/www/apps/Desktop/Ch_10_Photosynthesis/10-17-LightReactions.mov


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Cyclic Electron Flow

Calvin Cycleuses up more ATP than NADPH

so cyclic electron flow helps to generate more

ATPs

Short circuite- fall back from P700 primary

electron acceptor to the 1stETC to generate

more ATPs via chemiosmotic phosphorylation


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Tipe-tipe Fotosintesis

Berdasar produk paling awal dari fiksasi CO2 udara:

Tipe C-3 Tipe C-4

Tipe CAM: terjadi pada tumbuhan gurun,

Karakter gurun:1) Siang sangat terik, malam sangat dingin

2) Lingkungan (Udara & tanah) sgt kering

Adaptasi :1) Struktural: Stomata tersembunyi (kriptofor, sunken), Sukulen

2) Fisiologis :

= Stomata membuka pada malam hari= Fiksasi CO2 pada malam hari, dibentuk asam malat

dan ditimbun di vakuola

= Fotosintesis tipe CAM, proses di malam & di siang hari


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Struktur Anatomi Daun Jagung (C4)


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Fotosintesis Tipe C4


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Tahapan fotosintesis C4

PEP-Case

dehidroge

nase


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Fotosintesis CAM

PEP-Case


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Perangkat Fotosintesis C-3 & C-4

No Hal Tbhn C3 Tbhn C4

1 Daur Calvin Ada, di stroma

kloroplas mesofil

Ada, di stroma sel

seludang berkas

2 Penerima CO2 udara Ru-dP PEP

3 Enzim pengikat CO2 udara RubisCo PEP-karboksilase

4 Produk awal fiksasi CO2 As. Fosfo-gliserat[ PGA ]

As. Oksaloasetat[ OAA ]

5 Daya ikat karboksilase thdp

CO2

Sedang Kuat

6 Tempat fotosintesis Mesofil saja Mesofil & seludang

berkas

7 Kloroplas Satu jenis 2 Jenis

8 Penghambatan oleh O2

( Fotorespirasi )

Besar Kecil


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Organisme

Ototrof

Khemo-ototrof

Foto-ototrof

Jenis bakteri ttt

Cyanobakter

(bluegreen algae)

Eukariot

Prokariot

Tumbhn Tinggi

Algae

makroskopis

Algae bersel 1

Bakteri ttt

1. Pseudomonas

2. Thiobacillus fero-0xidans

3. Thiobacillus thio-oxidans

4. Nitrosomonas

5. Nitrobacter

Fotosintesis

Kemosintesis


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Contoh kemosintesis

Pseudomonas : 6H2 + 2O2 + CO2 5 H2O + CH2O(materi sel)

Thiobacillus : FeCO3 + O2 + 6H2O Fe(OH)3 + 4 CO2 + Materi sel

fero-oxidans

Thiobacillus : H2S2O3 + O2 2H2SO4 + Materi sel

thio-oxidans

Nitrosomonas : 2NH3 + 3O2 2HNO2 + 2 H2O + Materi sel

Nitrobacter : 2HNO2 + O2 2 HNO3 + Materi sel

Kemosintesis : Sintesis materi sel (bahan organik) dengan energi dari hasil

oksidasi zat-zat anorganik


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Light-independent reactions

(Dark Reactions)


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The Calvin/Benson/C3 cycle

Has 3 phases:

1. carbon fixation phase(FIKSASI KARBON)

2. reduction of CO2 phase(REDUKSI CO2)

3. regeneration of RuBP phase(REGENERASI

RuBP)


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carbon fixation phase


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each CO2molecule is attached to a five-carbon

sugar, ribulose bisphosphate (RuBP)

catalyzed by RuBP carboxylase or rubisco

six-carbon intermediate splits in half to form

two molecules of 3-phosphoglycerate


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reduction of CO2

phase


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each 3-phosphoglycerate receives anotherphosphate group from ATP to form 1,3bisphosphoglycerate.

pair of electrons from NADPH reduces,Gain,each 1,3 bisphosphoglycerate to G3P.

Electrons from NADPH change a carboxylgroup to a carbonyl group.

i f R BP h


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regeneration of RuBP phase


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regeneration of the CO2acceptor (RuBP),

these five G3P molecules are rearranged to

form 3 RuBP molecules.

cycle must spend 3 more molecules of ATP

(one per RuBP) to complete the cycle and

prepare for the next.


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Hatch & Slack/C4 cycle

Inefficient as RUBISCO can act as both a carboxylase

and as an oxygenase.

Oxygenase activity leads to loss of carbon that has

already been fixed. Some plants have an alternative pathway where CO2

is first fixed into C4 organic acids (C4 pathway) and

then liberated later to undergo the Calvin/Benson

cycle (C3 metabolism).


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2 types of C4 cycle:

1. C3 and C4 metabolism are separated in space

(different cells) e.g. sugar cane

Characteristic aggregation of cells around thevascular bundles - Krantz morphology (C4 cycle)

2. C3 and C4 metabolism are separated in time (same

cell=mesophyl) e.g. pineapple (CAM cycle).

Comparison of C3 & C4 leaves


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C3 - note the lack of

chloroplasts in the

bundle sheath

C4 - note the extensive

chloroplasts in the bundle

sheath

CO2


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Separation

in space (C4 cycle)

Vascular tissue

Malat

Bundle sheath cell

Mesophyll cell

surrounding

bundle sheath

CO2

PEP (3C)

C3CO2

OAA (4C)

Pyruvate (C3)

ATPADP

sugar

CO2


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Separation

in time (CAM cycle)

Mesophyl

Malat

In the light

In the dark

CO2

PEP (3C)

C3CO2

OAA (4C)

Pyruvate (C3)

ATPADP

sugar



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p

Details of C4 cycle


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y

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